Error: String reference not set to an instance of a String. Parameter name: s

Dear Colleagues,

I have a problem with SDL Studio 2019. I used trial version for about 20 days, then tried to activate my license (upgraded from Studio 2017), and it returns this error after I select 5 languages. Looks like the error is not with SDL. I tried several options, re-installed several times, deleted previous SDL version folders in Roaming, AppData etc. Nothing helped.

I tried both SDLTradosStudio2019_SR2_15.2.7.2849.exe and SDLTradosStudio2019_SR2_15.2.6.2831.exe (just for the experiment sake)

Attaching below the error xml.

<SDLErrorDetails time="17.08.2020 10:15:11">
  <ErrorMessage>String reference not set to an instance of a String.
Parameter name: s</ErrorMessage>
  <Exception>
    <Type>System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
    <ParamName>s</ParamName>
    <HelpLink />
    <Source>mscorlib</Source>
    <HResult>-2147467261</HResult>
    <StackTrace><![CDATA[   at System.Text.Encoding.GetBytes(String s)
   at Sdl.TranslationStudio.Common.Licencing.FreelanceSelections.set_ConfiguredLanguages(List`1 value)
   at Sdl.TranslationStudio.Common.SetupWizard.LanguageChoiceWizardPageControl.UpdateData()
   at Sdl.TranslationStudio.Common.SetupWizard.LanguageChoiceWizardPage.OnNext()
   at Sdl.Desktop.Platform.Wizard.AbstractInternalWizardPage`1.OnFinish()
   at Sdl.Desktop.Platform.Wizard.AbstractWizard`1.Finish()
   at Sdl.Desktop.Platform.Wizard.AbstractWizard`1._form_Finish(Object sender, CancelEventArgs e)
   at Sdl.Desktop.Platform.WPF.ViewModel.WPFWizardFormViewModel`1.Execute_FinishCommand()
   at Sdl.Desktop.Platform.MVVM.DelegateCommand.<>c__DisplayClass1_0.<.ctor>b__0(Object x)
   at Sdl.Desktop.Platform.MVVM.DelegateCommand`1.Execute(Object parameter)
   at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at System.Windows.Window.ShowHelper(Object booleanBox)
   at System.Windows.Window.Show()
   at System.Windows.Window.ShowDialog()
   at Sdl.Desktop.Platform.WPF.ViewModel.WPFWizardFormViewModel`1.ShowDialog(IWin32Window owner)
   at Sdl.TranslationStudio.Common.SetupWizard.SetupWizardLauncher.Execute()
   at Sdl.Desktop.Platform.Implementation.Studio.ExecuteStartupExtensions(ISplashScreen splashScreen)
   at Sdl.Desktop.Platform.Implementation.Studio.Run(ISplashScreen splashScreen, IEventAggregator eventAggregator)
   at Sdl.TranslationStudio.Application.Launcher.RunApplication()]]></StackTrace>
  </Exception>
  <Environment>
    <ProductName>SDL Trados Studio</ProductName>
    <ProductVersion>15.0.0.0</ProductVersion>
    <EntryAssemblyFileVersion>15.2.6.2831</EntryAssemblyFileVersion>
    <OperatingSystem>Майкрософт Windows 10 Домашняя для одного языка</OperatingSystem>
    <ServicePack>NULL</ServicePack>
    <OperatingSystemLanguage>1049</OperatingSystemLanguage>
    <CodePage>1251</CodePage>
    <LoggedOnUser>DESKTOP-CEC6B6Q\Optimus</LoggedOnUser>
    <DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
    <ComputerName>DESKTOP-CEC6B6Q</ComputerName>
    <ConnectedToNetwork>True</ConnectedToNetwork>
    <PhysicalMemory>8270668 MB</PhysicalMemory>
  </Environment>
</SDLErrorDetails>

Thanks in advance,

Georgy